In the past, genetic analysis of different influenza viruses has been directed toward the characterization of the surface proteins hemagglutinin and neuraminidase. Recently developed methods for analysis of single stranded RNAs on polyacrylamide gels have provided a powerful tool to characterize not only the hemagglutinin and neuraminidase genes but all 8 genes of influenza viruses. The following plan is aimed at a more precise genetic analysis of influenza viruses. 1) A catalogue of the RNA patterns of the influenza A viruses isolated during the last 4 pandemic periods and of viruses isolated in the future will be established; these RNA patterns will be compared to those of prototype viruses isolated from pigs, horses and birds in order to more fully understand the nature of genetic variation observed with influenza A viruses. 2) Maps of the genomes of human influenza A viruses of all 4 pandemic periods and of selected animal strains will be established following recently developed procedures. Attempts will also be made to establish genetic maps for influenza B and possibly for influenza C viruses and to characterize their RNAs. 3) The fine structure of certain RNA segments will be investigated in order to make more meaningful comparisons between some of the influenza virus strains. This will be accomplished by oligonucleotide maps of the RNA segments and examination of corresponding gene products by gradient polyacrylamide gel electrophoresis and peptide mapping. 4) The genetic composition of selected influenza virus strains (e.g., vaccine strains, attenuated strains, future isolates) and of recombinant viruses derived from well characterized laboratory strains will be examined to correlate their gene composition with biological properties.